The present invention relates to a mixed phase container, e.g., a fluidized bed type olefin polymerization reactor and, more particularly, is concerned with a device for detecting coagulations or chunks produced in the mixed phase container.
When a mixed phase container, e.g., a fluidized bed type olefin polymerization reactor, is used for a long period of time, coagulations are produced in the container and may be attached on the inner surface of the side wall of the container. Various techniques have been devised heretofore to detect such a coagulation. One known technique is to utilize radiation, as described in, e.g., U.S. patent application Ser. No. 160,288, filed on Jun. 12, 1980 by John Mitchell Jenkins, 3rd, et al, now U.S. Pat. No. 4,371,977.
According to this technique, a radiation source is arranged at the center of the container, and a plurality of radiation detectors are arranged around the container. When a change in density of the mixed phase between the radiation source and the detectors is detected, the presence and size of a coagulation can be recognized. In this technique, it is possible to use a radiation source having a considerably high-level radiation of about 1,000 mCi.
Generally, a mixed phase container, e.g., a fluidized bed type olefin polymerization reactor is huge and of substantially cylindrical shape, which has a diameter of several meters and a height of ten to twenty meters. When the container is clogged, it is usual that an operator enters the container to remove the clogging object. Also, the operator enters the container to perform periodic inspections. Accordingly, if a radiation source is arranged in the reactor, very strict consideration must be paid to ensure the safety of the operator in the container. Also, a high-level technique is needed to ensure safety against earthquake or fire. In view of these respects, the conventional technique using the radiation as described above is not practical.
In addition, the size of the smallest detectable coagulation is limited in this technique using radiation. Therefore, a need exists to improve the capability for detecting smaller coagulations to prevent clogging in the container more reliably.
In order to resolve these problems, simple means of using an observation glass window which is mounted on the side wall of the container was suggested. In fact, however, it is difficult to visually observe coagulations through the observation glass window because the field of view is interfered with by the substance in the mixed phase container.